Thermionic tube



April 17, 1934- J BETHENOD 1,955,404

THERMIONIC TUBE Filed May 27, 1927 We? f2 INVENTOR JOSEPH BETHENUD 124 AT R NEY Patented Apr. 17, 1934 UNITED STATES THERMIONIG TUBE Joseph Bethenod, Paris, France Application May 27, 1927, Serial No. 194,610 In France May 28, 1926 2 Claims.

The present invention relates to thermionic tubes, and more particularly to vacuum tubes containing five electrodes, namely, a filament, two grids and two plates, and its applications.

In the copending application, Serial No. 175,998, filed on March 17, 1927 in the name of Ilia Podliasky now Patent No. 1,330,175, a thermionic tube comprising four electrodes has been disclosed which, fundamentally, consists of a heated filament, a perforated electrode or grid, and two non-perforated electrodes or plates. These different elements are preferably disposed in the form of concentric cylinders in the order here indicated, the filament being ordinarily mounted, as is well known, in a way so as to be located exactly, or practically so, along the axis of the system. According to the arrangements there shown, the input circuit (or control circuit) is connected between the grid and the outer plate, while the output circuit is united with the filament and the second plate. In this way, the two circuits have generally no point in common between them.

N ow, according to the present invention, a grid is added to the above assembly so that there are five electrodes contained within the evacuated tube. In the drawing:

Figure 1 shows by way of example a cross'sectional view of one embodiment of the invention, the section being taken at right angles to the tube axis.

Figures 2 and 3 are similar views of other embodiments of the invention.

Figure 4 illustrates the five electrode tube in connection with a circuit arrangement for amplifying radio frequency or audio frequency currents, and

Figure 5 shows the tube with circuit connections for operating as a frequency changer.

Referring particularly to Figure l, the wall or envelope of the tube is denoted by 1, while 5 stands for the outer cylindrical plate, 2 the secend plate, the two grids being indicated diagrammatically at 3 and 6. The incandescible filament 4 may be constituted in any desired or convenient way; it may also be made up of several wires coupled together in series or in parallel, etc. A tube constructed in a way as hereinbefore disclosed may be adapted to a number of uses, for instance, for detection, radio frequency or audio frequency amplification, wave generation, etc., as shown in the drawing. For example, in Figure 4 there is shown the five electrode tube in accordance with my invention, associated with circuit elements for the amplification of radio or audio frequency currents, the currents to be amplified being applied to the input circuit connected between the electrodes 5 and 6, and the amplified currents appearing in the output circuit connected between the electrodes 4 and 6. The grid electrode 3 is connected to the output circuit as shown.

In Figure 5, which illustrates a frequency changer arrangement the electrodes 5 and 6 are connected with radio receiver apparatus, and the electrodes 2, 3 and 4 are employed to form a self-exciting local oscillator of the known triode type. There will then be obtained in the circuit of the anode or plate 2 a current having a frequency (f1f2) corresponding to the difference between the frequency (ii) of the potential applied between 5 and 6 and the frequency (f2) of the local generator. In this way, a frequency changer operating at high efficiency is obtained. If, on the contrary, the local generator forms a part of a radio transmitting system, the same circuit arrangement allows of modulation by a telephone current of very low power. The tube may also be used in circuit arrangements and schemes disclosed in the above-mentioned copending application, the supplementary grid being united with a source impressing thereon a definite potential compared with the filament. Moreover the roles of the grids 3 and 6 may be inversed, if desired, in all cases.

In Figure 2 there is diagrammatically shown another mode of construction of the pentode. The electrode 5 is placed in the center of the system. The same may consist of a member disposed between two filaments 4, for instance, V-fashion. In the case of power tubes the number of filaments may be augmented so as to form a drum arrangement, and the electrode 5 may then be given a cylindrical shape, as shown in Figure 3.

Having thus particularly described my invention, I claim:

1. An electron-discharge device comprising a cathode, a tubular perforate electrode mounted about said cathode, a second tubular perforate electrode mounted about said first tubular perforate electrode, a tubular imperforate electrode mounted about said second tubular perforate electrode, and a second tubular imperforate electrode mounted about said first tubular imperforate electrode.

2. An electron discharge device having in combination an electron emitting cathode, inner and outer cylindrical grid electrodes, and inner and outer cylindrical plate electrodes, all of said cy- 

